Maisie Williams, who plays Arya Stark on HBO's Game of Thrones, knows not to give away the plot of the show's long-awaited final season. But then again, she's only 21, and actresses make mistakes.

Williams, sporting some pink cotton-candy hair, appeared on The Tonight Show Starring Jimmy Fallon on Monday night and revealed her top five moments playing Arya. No surprises there: dad Ned's death, reuniting with Sansa, that kind of thing.

But when Fallon nudged her for a real spoiler, Williams appeared to deliver on a whopper. But watch the whole thing and remember Monday's date, April 1.